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AX2500/2850 Motor Controller User’s Manual 61
Connecting User Devices to Analog Inputs
Using these resistor values, it is possible to measure a voltage ranging from -5V to +60V
with a 0.25V resolution. The formula for converting the A/D reading into a voltage value is
as follows.
Measured volts = ((controller reading + 128) * 0.255) -5
Note: The A/D converter’s reading is returned by the ?p command and is a signed 8-bit
hexadecimal value. You must add 128 to bring its range from -127/+127 to 0/255.
Connecting User Devices to Analog Inputs
The two analog inputs can be used for any other purpose. The equivalent circuit for each
input is shown in Figure 34. The converter operates with an 8-bit resolution, reporting a
value of 0 at 0V and 255 at +5V. Care should be taken that the input voltage is always posi-
tive and does not exceed 5V. The converter’s intrinsic diodes will clip any negative voltage
or voltage above 5V, thus providing limited protection. The value of the analog inputs can
be read through the controller’s RS232 port.
47kOhm
10kOhm
47kOhm
47kOhm
4.7kOhm
AX2500 Internal Resistors
and Converter
To Battery
+ Terminal
+5V 14
10
or 11
Ground 5
A/D
FIGURE 33. Battery voltage monitoring circuit
47kOhm
10kOhm
47kOhm
+5V 14
Ground 5
A/D
Input Ana 1 11
or Ana 2 10
FIGURE 34. AX2500/2850 Analog Input equivalent circuit